Yeah, that makes sense. So he could call an election before he gets officially booted, if he hears rumblings of mutiny.
Then presumably he's told them he will do this. But they'd all need to think he's mad enough to do it.
There again, he'd get a £115k a year tax-free pension and never need to work again. Not sure what an everyday MP or cabinet member gets, probably little or nothing. So perhaps it is a credible threat. Former PMs always look very sad as back-benchers, it must be a terrible climb-down for them.
Whether he calls an election or not, he's probably permanently destroyed the Labour party anyway, so his legacy doesn't really matter.